In a cut-off die set of the double-cut type a notching blade is caused to move across and notch the upper surface of the tubing prior to the entry of a shearing blade into the upper tube wall. Prenotching the tube in this manner reduces or eliminates dimpling or collapsing of the tube wall by the shearing blade, thus eliminating the need for reshaping the ends of the tubing after the cutting operation.
The notching apparatus typically comprises a notching blade fixed or mounted to a carriage member mounted to the cross slide assembly of the cut-off die set. Cross slide assemblies are known, see U.S. Pat. No. 4,766,792. The cross slide assembly is operated by the upper platen of the die set by way of a mechanical cam and cam follower. The association is such that vertical travel of the upper platen of the die set causes the notching blade to travel through a transverse path perpendicular to the axial path of the tube. Both thrust and "pull across" motions are known. See for example U.S. Pat. Nos. 4,109,555 and 4,294,147.
The notching blade which performs the cutting operation eventually succumbs to wear and must be replaced. Presently, in order to replace notching blade, the worn blade must be unbolted from the carriage and a new blade rebolted in its place.
Time is of the essence in the tube cutting industry, tubing continuously emanates from a tube mill at a high rate of speed. Thus any problems, delays or shutdowns for repair or replacement of the cutting equipment results in lost production and revenue to the tube maker. Therefore any time savings that result from ease in maintenance and/or replacement of parts increases the period the mill can be operational, thus increasing production.